The present invention is directed to flow meters which are used to measure the amount of fluid being dispensed or pumped. More particularly, the present invention is directed to flow meters which are precalibrated to accurately meter the flow of a variety of different fluids. The present invention is further directed to air flow compensators which compensate fluid flow measurements for air that passes through flow meters.
There are inherent internal leakage or xe2x80x9cslippagexe2x80x9d problems which effect the accuracy of flow meters, particularly volume displacement meters. Fluid which leaks or xe2x80x9cslipsxe2x80x9d by the mechanical structures intended to monitor fluid flow does not contribute to the counting mechanism and thus must be accounted for by other means, such as adjusting gear ratios on mechanical counters or multiplying factors on electronic readouts.
The main cause of variation in the amount of slippage is the viscosity of the fluid. Thin or less viscous fluids tend to experience a greater amount of slippage than thick or more viscous fluids. Accordingly, for best accuracy, flow meters must be calibrated whenever fluid viscosities change significantly. In addition to varying between different fluids, viscosities can vary over temperature ranges.
Present flow meters are either precalibrated for a particular fluid or otherwise designed to be field calibrated. Precalibrated flow meters have the disadvantages of being limited for use with a particular fluid viscosity, and not being able to compensate for temperature related changes in viscosity. Field calibrated flow meters require pumping or dispensing of a small quantity of a fluid during calibration. This can present problems when using hazardous or expensive materials since the meter will not accurately measure the volume of fluid used to calibrate the meter. Moreover, containment or recovery of the volume of fluid used to calibrate the meter may be awkward, particularly if the fluid to be dispensed is stored in a container equipped with one-way valves which prevent the user from putting fluid back into the container.
The present invention provides for precalibrated flow meters which allow a user to accurately dispense or pump a variety of fluids without recalibrating the meter for each fluid. Moreover, the present invention provides air flow compensators which are used in conjunction with precalibrated flow meters to compensate fluid flow measurements for air or gas that passes through the precalibrated flow meters.
According to other features, characteristics, alternatives and embodiments which will be understood as the description of the present invention proceeds, the present invention provides an air flow compensator which includes:
a main slide element having a magnetic insert in one end thereof;
a proximity sensor for detecting the proximity of the magnetic insert;
a secondary slide element;
a first spring element that biases both the main slide element and the secondary slide element away from the proximity sensor; and
a second spring element that biases only the secondary slide element away from the proximity sensor.
The present invention further provides an air flow compensator which includes:
a fluid flow passage having an inlet end and an outlet end;
a proximity sensor positioned adjacent the outlet end of the fluid flow passage;
a main slide element having a magnetic element in one end, the main slide element moveable between a first position in which the magnetic element is spaced away from the proximity sensor and a second position in which the magnetic element is near the proximity sensor;
a secondary slide element positioned on the main slide element for movement therewith and for independent movement along the main slide element, the position of the secondary slide element within the fluid flow passage being determinative of the amount of fluid that can flow therethrough;
a first spring element that biases the secondary slide toward the inlet end of the fluid flow passage; and
a second spring element that biases the main slide element toward the inlet end of the fluid flow passage.
The present invention also provides a precalibrated flow meter which includes:
a body having an inlet and an outlet;
a fluid driven element within the body that moves in response to fluid flow between the inlet and the outlet;
a memory storage device for storing a plurality of calibration factors which correspond to different fluid viscosities;
means for selecting one of the plurality of calibration factors;
means for calculating fluid flow between the inlet and the outlet from the selected one of the plurality of calibration factors;
an air flow compensator in the inlet of the body, the air flow compensator including:
a cartridge body having an inlet end and an outlet end;
a proximity sensor positioned adjacent the outlet end of the cartridge body;
a main slide element having a magnetic element in one end, the main slide element moveable between a first position in which the magnetic element is spaced away from the proximity sensor and a second position in which the magnetic element is near the proximity sensor;
a secondary slide element positioned on the main slide element for movement therewith and for independent movement along the main slide element, the position of the secondary slide element within the cartridge body being determinative of the amount of fluid that can flow therethrough;
a first spring element that biases the secondary slide toward the inlet end of the cartridge body; and
a second spring element that biases the main slide element toward the inlet end of the cartridge body; and
means for compensating the calculated fluid flow for air detected by the air flow compensator which passes through the cartridge body.